Tools and Inquiry — IB Physics skills
I.2.1 Collecting data in Physics — IB Physics HL Revision Notes & Topical Questions
5 min read 8 parts Lesson 18 of 22 1 quiz
Lesson summary
I.2.1 Collecting data in Physics — IB PHYSICS SL notes: Collect sufficient quantitative and qualitative data, record it correctly and respond to problems during data collection.This is the "doing" phase — performing the experiment that was designed.The goal is high-quality raw da…
- It involves precise measurements and recording all relevant information
- Quantitative data
- The raw data table is the foundation of the report
- At least three repeat trials for each increment
- Record raw readings directly
- Observations are evidence
Part 1 of 6Aim of data collection
1This is the "doing" phase
- This is the "doing" phase performing the experiment that was designed.
2
The goal is high-quality raw data that is accurate and sufficient to answer the research question.
3It involves precise measurements and recording all relevant information
- It involves precise measurements and recording all relevant information numbers and observations.
Part 2 of 6Raw data table
1Quantitative data
Quantitative data numerical data that you measure.
2The raw data table is the foundation of the report
- The raw data table is the foundation of the report it is the first table and holds only direct measurements, with no calculations.
3
Design the table before starting.
- A specific title describing the experiment.
- Clearly labelled columns for the independent and dependent variables.
- Units and uncertainties in the column headers, not in the body of the table.
4
Record to the precision of the instrument.
- A metre rule marked in millimetres gives readings such as 0.550 m (three decimal places).
- A digital multimeter reading to two decimals gives 5.00 V, not 5 V.
Part 3 of 6Sufficient data
1
Enough data points to see a trend.
2
At least five increments of the independent variable.
3At least three repeat trials for each increment
- At least three repeat trials for each increment to ensure reliability.
4Record raw readings directly
- Record raw readings directly never do calculations in your head or on scrap paper.
Part 4 of 6Qualitative observations
1Qualitative data
Qualitative data non-numerical data observed during the experiment.
2
It gives context and helps explain unexpected results or errors.
3
Examples in physics.
- A pendulum swinging in a slight ellipse instead of a plane.
- A flicker on a digital multimeter showing an unstable reading.
- A wire or component warm to the touch, showing heat dissipated in a resistance.
- A laser beam spreading as it passes through a narrow slit.
4Observations are evidence
- Observations are evidence they can be used in the conclusion and evaluation.
Part 5 of 6Dealing with issues during collection
Dealing with issues during collection
Notice and respond to problems as they happen
- Notice and respond to problems as they happen do not ignore them, and record them in the lab notes.
Unstable readings.
- Wait for the reading to settle, or record the central value and estimate the fluctuation as an uncertainty.
- Record how it was handled.
Anomalous result (outlier).
- Record it, then do an additional trial to get a reliable set.
- Do not erase it — its exclusion is justified later.
Difficulty in measuring (e.g. an oscillating spring).
- Make a note — it is a limitation of the method to discuss in the evaluation.
Poor contacts
- Poor contacts clean and re-attach connections to get stable readings.
Part 6 of 6More from the specification
1
Period Measurement and Averaging
- Measuring the time for multiple complete oscillations of a simple pendulum of fixed length and dividing by the cycle count yields an accurate average period with minimal reaction error.
2
Data Processing and Significant Figures
- Recorded experimental data must be tabulated systematically and processed to significant figures consistent with the instrument's measurement uncertainty.
3
Linearizing Graph Relationships
- Plotting period squared (T2 against pendulum length (L) produces a straight-line graph, confirming the theoretical power relationship and allowing gravitational acceleration g to be evaluated from the slope.
4
Graph Plotting Conventions
- Data points and uncertainty error bars are plotted with the independent variable on the x-axis and the dependent variable on the y-axis to construct lines of best fit.
5
Simple pendulum
- A small bob on a light string of length L
6
Random error
- An unpredictable variation in readings, reduced by repeating and averaging.
7
Length
- Resistance is directly proportional to the length of a wire.
8
Period
- Time for one revolution.
9
Current
- Flow of electrons in a circuit.
10
Gradient
- Slope of a graph line.
11
Potential difference
- Work done by a unit charge passing through a component.
12
Significant figures
- Digits carrying meaningful information in a number.
13
Percentage uncertainty
- The absolute uncertainty divided by the value, times 100%.
14
Absolute uncertainty
- The range ±Δx in the same unit as the measurement.
Key terms
| Term | Meaning |
|---|---|
| Raw data | Direct measurements recorded without calculation. |
| Quantitative data | Numerical data that is measured. |
| Qualitative data | Non-numerical observations. |
| Anomalous result | Result that does not fit the pattern of the others. |
| Repeat trial | Repetition of a measurement to improve reliability. |
| Resolution | Smallest change an instrument can show. |
Avoid these mistakes
1
Putting calculations in the raw data table.
2
Writing units after every number instead of in the column headers.
3
Recording readings with fewer decimal places than the instrument allows.
4
Deleting an outlier instead of recording it and repeating the trial.
5
Ignoring qualitative observations that explain unexpected results.
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